This invention relates to a liquid dispersion or emulsion formulation containing an active silicone material. By an active silicone material we mean a silicone conferring a desired benefit to a medium in which it is incorporated. In particular the invention relates to a liquid dispersion or emulsion formulation which can be dispersed in a secondary liquid medium and in which the benefits of the active silicone material are increased by slowing the rate of dispersion or release of the silicone into the secondary medium.
The active silicone material can for example be a silicone antifoam. Slow release of that antifoam in the foaming medium can provide greatly increased performance and high persistency.
An antifoam or foam control agent is a material which, when added in low concentration to a foaming liquid controls problems of excess or undesired foam. The antifoam equilibrates the rate of foam collapse with the rate of foam formation and can remove unsightly and troublesome surface foam, and improve filtration, watering, washing and drainage of various types of suspension, mixtures, and slurries. Antifoams are used for example in the pulp and paper industry, paints and latex coating processes, fertilizers, textile cleaning, dying and treating, fermentation processes, metal working, adhesives, caulk and polymer manufacture, food processing such as sugar extraction from sugar beet, oil extraction, cooling towers, and in municipal and industrial water treatment as well as in liquid or solid detergent compositions.
In many of the above uses an aqueous stream can move through a process or plant providing many opportunities and locations for foam to form, for example when pumping or washing and in sluice ways. Pumping foam control agents into the stream at each position of foam generation can be problematic and expensive.
Encapsulated and slow release antifoams are described in the literature. For example there are a variety of granulated materials described which are claimed to have delayed release properties. U.S. Pat. No. 4,894,177 describes a delayed release granulated antifoam for laundry detergents where the antifoam is contained on a water soluble cellulose material. EP-A-924250 describes a granulated antifoam contained on starch including a waxy coating that delays release. EP-A-206522 describes an antifoam granule that is coated with silicone oil or wax which disrupts in water. EP-A-210731 describes a finely divided antifoam containing silicone and hydrophobic silica with a high melting point organic such as a monoester of glycerol and fatty acid and describes the process for granulation of the combination on a fluidized bed. U.S. Pat. No. 5,318,718 teaches a process for forming granular antifoam powder on phosphate free cellulosic carriers with a wax and silicone components.
U.S. Pat. No. 5,773,407 describes the formation of a cross linked coating on the exterior of emulsified silicone antifoam droplets by reaction with reactive silanes. Slow release benefits in laundry applications are claimed. JP-A-55-100309 describes the use of a protein encapsulated silicone antifoam that is released during tooth brushing.
In U.S. Pat. No. 4,411,933 ethyl cellulose is coated on the outside of alkylpolysiloxane droplets from a cyclohexane dispersion.
A silicone composition according to the present invention comprises a continuous phase of a polar organic liquid having dispersed therein particles of a silicone active material encapsulated within an organic encapsulating material which is solid at 25xc2x0 C., is sparingly soluble in the polar organic liquid at 25xc2x0 C. but is substantially dissolved in the polar organic liquid at an elevated temperature in the range 40-100xc2x0 C., wherein the three phase contact angle between the organic encapsulating material , the silicone antifoam, and the polar organic liquid, with the angle measured through the silicone, is below 130xc2x0.
The invention includes a foam control composition comprising a continuous phase of a polar organic liquid having dispersed therein a polyorganosiloxane fluid combined with a surfactant of HLB below 8 and a hydrophobic silicaceous material.
A preferred process according to the invention for the production of an encapsulated silicone composition comprising (i) dispersing a silicone active material, a solid organic encapsulating material and a hydrophobic silicaceous material in a polar organic liquid with shear so that the average silicone particle size is less than 0.5 mm, the temperature of the dispersion being sufficiently high that the said organic encapsulating material is dissolved in the composition; and (ii) cooling the dispersion to deposit the organic encapsulating material onto the interface of the silicone particles while agitating sufficiently to maintain the silicone particle size below 0.5 mm.
The encapsulation of the silicone in the form of droplets within a matrix or shell of the solid organic encapsulating material that is moderately soluble in the secondary liquid medium enables the benefits of that silicone to be increased by slowing the rate of dispersion or release of the silicone into a secondary liquid medium which has a foam problem.